70 hp, 1974 evinrude connecting rods

[inohv8]

Hi Guys and Gals..<br />one of my winter projects is re-building the 70 hp, I picked up for parts or repair.. so I took the repair for something to do..<br />the block has been re-bored, and lapped. all the parts have been gotten.. here is the problem..<br />my marine place who carries the Sierra pistons, do not carry the pistons for the 1974, after checking. I found out that the original pistons had a wrist pin measuring .625 diameter and the sierra pistons use the standard .75<br />So, I now have pistons with the 3/4 wrist pins as I bought for the next year (same piston size).. I have 3 connecting rods for the smaller pins, I got the needle bearings for the 3/4 inch hoping that it might work out, but alas it did not..<br />Now I have an option (somewhere in this world is what I need), do I get the wrist pin holes on the rods machined to fit the new pistons and bearings?<br />here is some spec. the wrist pin hole of the rod right now is .873. I would have to get it opened up to 1.06, the OD of the rod is 1.26", I don't feel good about taking off so much meat but where can I get some rods? that will fit the larger pin?<br />any suggestion? or is this project destined for a spare parts bin?<br />tks for reading this.. I hope I explained myself alright...

 

[DHPMARINE]

Re: 70 hp, 1974 evinrude connecting rods

What rods does Sierra offer for the pistons you bought?I agree,don't open up the holes on the rods you have.I also doubt sleeving the pistons down to .625 would be anything to relie on.<br /><br />DHP

 

[Laddies]

Re: 70 hp, 1974 evinrude connecting rods

Wiseco makes pistons and a bearing kit to adapt to that engine.

 

[inohv8]

Re: 70 hp, 1974 evinrude connecting rods

To answer both questions and statements..<br />1stly Sierra does not offer the rods anymore and they do not offer the pistons either.. I was told by a fellow who is knows engines inside/out that they went to the larger wristpins for strenght and durability considering the HP rating and dependability is the #1 concern.<br />Regarding Wiseco pistons, they do have a piston kit available however OMC went to the larger pin for reason and would rather go that way.. after all, if I am spending the time and money to do a perfect build, I would like to go all the way.. <br />I did find an outfit in the U.S. who has rods (new and used), I will have to contact them and question the size and diameter of the meat and if available, I would like to go that way.. Unless you fine folks know of someone who a member here, I would rather purchase from them just for being an asset to this forim.

 

[seahorse5]

Re: 70 hp, 1974 evinrude connecting rods

Pro Marine Parts also sells pistons that will fit the early model rods on the 70hp.

 

[Chinewalker]

Re: 70 hp, 1974 evinrude connecting rods

Hi inohv8 ,<br /> Personally, I would find some good, used later style connecting rods to use with your pistons. The later rods are MUCH meatier and should work fine in your early block. I'm pretty sure the crankshaft end of the rods are the same diameter...<br />- Scott

 

[Dhadley]

Re: 70 hp, 1974 evinrude connecting rods

Yes, you can use the rods from a 1976 and newer 49 cid 3 cylinder. The 56 cid rods are different. <br /><br />The reason OMC went to the larger pins was that if the motor (with the early rods) was idled for extended periods the wrist pin may pound out on the middle cylinder. Either rod will work (pre 76 or 76 & newer) in your motor and the Wiseco piston will work on the early rod with the B1029 bearing kit.

 

[papasage]

Re: 70 hp, 1974 evinrude connecting rods

i have the same motor. iam looking for pistons . i bought a bunch of newer parts from a blown engin . the pistons would have worked but they wer left in a damp invirement and wer croded. now i am looking again . the 73&74 pistons have the top ring close to the top of the piston and the no led gass will deterate them . if you look at the newer piston aginst the 73&74 you wil see the top ring is lower on the newer ones . i am looking for some good used pistons . would take one 73 or 74 . and put it togather and run led substitute. all i wil do is run it for fishing . no long trips .i do have sone 3 cylinder parts if interested

 

[inohv8]

Re: 70 hp, 1974 evinrude connecting rods

do you know what size of the wrist pins? are they 1/2" or 3/4" that will tell me what rods you have... I think you have the smaller pins unless it was modified before..<br />Stan.

 

[inohv8]

Re: 70 hp, 1974 evinrude connecting rods

Well Guys, I think my answer is the get the heavier rods which apparentely were in the 1976 to 81 with the 3 inch standard bore.. I may have found a source of used and new ones in Quebec. They seem reasonable (I think) considering what the alternative is or even the cost of wiseco pistons. <br />let me know if they are reasonable, they want 75 bucks per rod at www.sports-marins-bf.com<br />I did not ask them if it was canadian or American.<br />lots of fun.....NOT!<br />Thanks for all you people's advice and comments..<br />Stan.

 

[Paul Moir]

Re: 70 hp, 1974 evinrude connecting rods

I got some hard to find NOS piston rings from those guys once - they were helpful and quick. <br /> The Marine Doctor in Saskatoon has a used parts dealer too. You should try to get a price from them as well. But $75CDN doesn't seem that bad to me - might want to find out what three cost.<br /><br />Any hope of finding the local outboard junkyard?